The present invention relates to a pilot controlled mechanism adapted to provide different rates of modulation depending upon the direction of movement for a manual control lever. More particularly, the pilot control mechanism is adapted to regulate operation of a rotatable winch drum through a power train including a normally engaged brake and a normally disengaged clutch.
For a winch unit of the type referred to above, it is common to provide for operator control over both reeling-in and reeling-out operation of the winch drum. For example, where the power train for the winch drum includes a normally engaged brake and a normally disengaged clutch, the brake may be gradually disengaged to permit reeling-out of cable from the winch drum while the clutch is selectively engaged in order to reel in cable upon the drum. The normally engaged brake may also be simultaneously disengaged along with engagement of the clutch.
When the winch unit is arranged upon a log skidder or similar machine, an operator may be required to perform a number of control functions for the vehicle, the winch unit and possibly other implements as well. Accordingly, it is desirable to provide a single control element for operating the power train for the winch unit to accomplish both reeling-in and reeling-out modes of operation.
A substantial load is normally secured to the cable during reeling-out operations of the type contemplated by the present invention. Accordingly, it is necessary to provide closely controlled modulation over disengagement of the brake in order to permit adequate operator control over the rate at which cable is reeled out from the drum.
Reeling-in of the cable is also accomplished with a load normally attached to the cable. However, since reeling-in of the cable is accomplished through a normally disengaged clutch, it is often desirable to provide for rapid modulation for engagement of the clutch as compared to disengagement of the normally engaged brake.